To be honest, he may be doing it without realizing it if he's under a lot of stress. He might just be snapping and taking it out on you because you're there. It doesn't make it right, but I would consider it forgivable as long as he's willing to work on fixing it. Hopefully it's something that can be solved.

To answer your specific question, make sure you guys are alone, for sure. Then just sit him down and say that you wanted to talk to him about something, definitely try to bring it up when he's relaxed so he's more likely to have an open mind. Then just tell him what you noticed and how it makes you feel. And express your concern and ask what's going on with him. Hopefully he'll just explain and work on being better at not directing his anger towards you.

No matter how much you love him, you deserve to be treated right and with respect. Just make sure you don't sacrifice too much out of love when you're getting crap in return.

Good luck, feel free to come back if you need help after the talk. :)

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kid, I wrote back,
all lovers betray.